TW201728927A - Polarizer and method for producing the same - Google Patents

Abstract

The present invention relates to a polarizer having a degree of orientation of 0.250 to 0.400, and a shrinkage force in absorption axis direction of 3.5 N/2mm or less, the degree of orientation being obtained by the following Equation 1: (Equation 1) degree of orientation= AMD- ATD / Alarge + 2 Asmall (in the equation, AMD is an absorbance of infrared light polarized in an absorption axis direction of the polarizer, ATD is an absorbance of infrared light polarized in a transmission axis direction of the polarizer, Alarge is the higher absorbance among AMD and ATD, and Asmall is the lower absorbance among AMD and ATD).

Description

Polarizer and manufacturing method thereof

The present invention relates to a polarizer and a method for producing the same, and more particularly to a polarizer which is excellent in optical characteristics and has a small contraction force in an absorption axis (extension) direction, and a method for producing the same.

A polarizing plate used in various image display devices such as a liquid crystal display device (LCD), an electric field emission (EL) display device, a plasma display device (PDP), an electric field emission display device (FED), an OLED, etc., is generally included in A polyvinyl alcohol (PVA) film adsorbs a polarizer having an iodine-based compound or a dichroic polarizing material, and has a polarizer protective film sequentially laminated on one side of the polarizer, and is further coated on the other side of the polarizer. A multilayered polarizer protective film, an adhesive layer bonded to other members, and a multilayer structure of a release film.

The polarizer constituting the polarizing plate is applied to an image display device, and in order to provide an image excellent in color reproducibility, it is basically required to have both high transmittance and polarization. In order to achieve this, a polarizer is produced by modifying a polyvinyl alcohol-based film itself or by using a non-sublimating dichroic dye instead of a sublimable iodine-based polarizing element.

On the other hand, the polarizer usually has a polarizing function by extending a film for forming a polarizer which is produced using a polymer, and aligning the internal molecules in a predetermined direction. Thus, the stretching step is an indispensable step in the manufacture of the polarizer.

However, such an extension step, when the polarizer is placed in a predetermined environment, becomes a cause of the contraction force in the direction of the extension (absorption axis), and the contraction force in the direction of the absorption axis becomes a cause of deformation of the polarizer. Therefore, reducing the contraction force in the direction of the absorption axis is an important consideration in the manufacture of an improved polarizer.

However, polarizers having high polarization and low shrinkage force have not been known so far.

In the Japanese Laid-Open Patent Publication No. 2010-145866, a method of manufacturing a polarizing sheet having a small shrinkage stress is disclosed, but an alternative to satisfy the above problem is not suggested.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-145866

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarizer and a method of manufacturing the same, which have a high degree of polarization and a small contraction force in the direction of the absorption axis.

A polarizer having an orientation of 0.250 to 0.400 and a contraction force in the direction of the absorption axis of 3.5 N/2 mm or less, wherein the orientation is obtained by the following formula 1: (Wherein, A _MD line of the polarizer than the absorbance of the infrared light absorption axis of the polarizer, A _TD-based absorbance of the polarizer in the transmission axis direction of the polarization of the infrared light, A _large line A _MD and in the A _TD The absorbance of the higher, A _small is the absorbance of the lower of A _MD and A _TD ).

2. The polarizer according to 1, wherein the orientation is 0.300 to 0.400.

3. A method for producing a polarizer comprising the steps of swelling, dyeing, stretching, crosslinking, complementary color and drying of a film for forming a polarizer, wherein the crosslinking step comprises extending the film for forming a polarizer to 2.00 to 3.00 times. a first crosslinking step and a second crosslinking step of extending the film for forming a polarizer to 1.00 times or less after the first crosslinking step, wherein the complementary coloring step is higher than an extension ratio of the second crosslinking step Further, the elongation ratio of the elongation ratio lower than the first crosslinking step is extended by the film for forming a polarizer.

4. The method of producing a polarizer according to the above 3, wherein the film for forming a polarizer is extended from 0.85 to 1.00 times in the second crosslinking step.

5. The method of producing a polarizer according to the above 3 or 4, In the above-described complementary coloring step, the film for polarizing film formation is extended from 1.01 to 1.25 times.

A polarizing plate comprising the polarizer described in the above 1 or 2, and a polarizer protective film bonded to at least one surface of the polarizer.

An image display device comprising the polarizing plate described in the above 6.

The polarizer of the present invention exhibits a contraction force in a predetermined range and a contraction force in the direction of the absorption axis, and exhibits a small contraction force in the absorption axis direction without deteriorating other physical properties and having excellent optical characteristics.

In the method for producing a polarizer of the present invention, the polarizer for forming a film of the present invention can be produced by extending the film for forming a polarizer in a specific range of elongation ratio in the crosslinking step and the complementary color step. In general, the higher the degree of extension, the higher the degree of alignment. Therefore, in order to achieve excellent polarization characteristics, the elongation ratio must be increased. In contrast, the higher the elongation ratio, the greater the contraction force in the direction of the extension (absorption axis). Therefore, the realization of the high alignment degree and the low contraction force in the absorption axis direction have a trade-off relationship, and it has not been known that a polarizer having a low refractive index and a low contraction force in the absorption axis direction is not known at present. According to the method for producing a polarizer of the invention, even when the contraction force is low in the direction of the absorption axis, the range of the alignment can be adjusted, and as a result, a polarizer having a high degree of polarization and having a small contraction force in the absorption axis direction can be produced.

The present invention relates to a polarizer having an alignment degree of 0.250 to 0.400 and a contraction force in the absorption axis direction of 3.5 N/2 mm or less, whereby the optical characteristics are excellent and the contraction force in the absorption axis direction is small.

Hereinafter, the present invention will be described in detail.

As described above, it is known that the high alignment degree of the conventional polarizer and the contraction force in the absorption axis direction are small, and an example of a polarizer which is excellent in the alignment degree and has a small contraction force in the absorption axis direction is not known.

However, the inventors of the present invention have produced a polarizer which satisfies both the high alignment degree and the contraction force in the absorption axis direction by the method for producing a polarizer having an adjustable alignment. Further, when the contraction force in the alignment degree and the absorption axis direction is adjusted to a specific range, a polarizer having a small degree of polarization and a small contraction force in the absorption axis direction can be obtained.

The polarizing plate of the present invention has an orientation of 0.250 to 0.400, preferably 0.300 to 0.400. When the degree of alignment is less than 0.250, the degree of polarization is lowered. When it exceeds 0.400, there is a problem that the contraction force in the absorption axis direction increases and the warpage of the polarizer becomes large.

In the present invention, in order to adjust the degree of alignment to the above range, the elongation ratio of the first crosslinking step can be adjusted to 2.00 to 3.00 times and the total cumulative stretching ratio can be adjusted to 5.0 times or more.

The alignment of the present invention can be obtained by the absorption of infrared light (IR) polarized by the polarizer in the direction of the absorption axis (MD direction), and the wear of the polarizer. The difference in absorbance of infrared light polarized in the direction of the through-axis (TD direction) is obtained. The specific relationship for obtaining a specific degree of alignment is as shown in the following formula 1.

(Wherein, A _MD based infrared absorbance of the polarizer in the polarization of the light, A _TD-based absorbance of the polarizer of the polarization of the infrared light, A _large tied transmission axis direction (TD direction) of the absorption axis direction (MD direction) A _MD and the absorbance A _TD in the higher, A _small line A _MD and in the lower of the absorbance A _TD).

The absorbance of infrared light can be measured, for example, by a Fourier Transform Infrared Spectrophotometer (FT-IR). The wave number of the infrared light can be set to, for example, 1290 cm ^-1 .

The polarizer of the present invention has a low contraction force in the absorption axis direction and a contraction force in the absorption axis direction of 3.5 N/2 mm or less. When the contraction force in the absorption axis direction is 3.5 N/2 mm or less, deformation of the polarizer can be effectively prevented. The lower the contraction force in the absorption axis direction, the lower the thickness is, and the lower limit thereof is not particularly limited, and may be, for example, 2 N/2 mm or more, 1 N/2 mm or more, or 0.1 N/2 mm or more. In the present invention, in order to adjust the contraction force in the absorption axis direction of the polarizer to the above range, the elongation ratio of the first crosslinking step can be adjusted to 2.00 to 3.00 times and the elongation ratio of the second crosslinking step can be adjusted to Adjusted below 1.00 times.

The polarizer of the present invention may have a thickness of 5 to 30 μm, preferably 10 to 28 μm, more preferably 15 to 26 μm. When the thickness of the polarizer is in the above range, both the low contraction force and the operability of the polarizer in the absorption axis direction can be achieved.

Further, the present invention provides a method of producing the aforementioned polarizer.

The method for producing a polarizer of the present invention comprises the steps of swelling, dyeing, stretching, crosslinking, complementary color and drying of the film for forming a polarizer, wherein the crosslinking step comprises extending the film for forming a polarizer to 2.00 to 3.00 times. And a second crosslinking step of extending the film for forming a polarizer to 1.00 times or less and relaxing the stress after the first crosslinking step, wherein the complementary coloring step is higher than the second crosslinking The extension ratio of the bonding step is longer than the extension ratio of the extension ratio of the first crosslinking step, and the film for polarizing film formation is extended. By adjusting the extension ratio of the cross-linking step and the complementary color step as described above, the refractive index of the polarizer and the contraction force in the absorption axis direction can be adjusted, and the contraction force in the high polarization degree and the absorption axis direction can be made small.

The method for producing the polarizer of the present invention will be more specifically described below.

The film for forming a polarizer for producing a polarizer, as long as it is a polymer film which can be used for the production of a polarizing plate, can be used without any particular limitation, and a film which can be dyed by a dichroic substance (for example, iodine), which is well known in the art, can be used. For example, a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film; a polyethylene terephthalate film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, a cellulose film, and the like A hydrophilic polymer film such as a partially saponified film; or a polyalked alignment film such as a dehydrated polyvinyl alcohol film or a dechlorination-treated polyvinyl chloride film. Among these, a polyvinyl alcohol-based film is preferred because it is excellent in the effect of enhancing the uniformity of the degree of polarization in the plane and the dyeing affinity for iodine is also excellent.

The method for producing a polarizer of the present invention may comprise swelling The step, the dyeing step, the crosslinking step, the complementary color step, the stretching step, the water washing step, and the drying step can be classified according to the extension method. For example, a dry stretching method, a wet stretching method, or a mixing stretching method in which the above two stretching methods are mixed may be mentioned. Hereinafter, the wet stretching method will be described as an example of the method for producing the polarizer of the present invention, but is not limited thereto.

In the above-described steps, the film for forming a polarizer can be carried out in a state of being immersed in a constant-temperature bath filled with a solution of one or more kinds selected from various types of solutions, except for the drying step.

<Swelling step>

In the swelling step, the unpolarized film for forming a polarizer is immersed in a swelling tank filled with an aqueous solution for swelling, and the impurities such as dust or an antiblocking agent deposited on the surface of the film for forming a polarizer are deposited. The step of removing the film for forming a polarizer, for improving the elongation efficiency, preventing the dye unevenness, and improving the physical properties of the polarizer.

For the aqueous solution for swelling, an aqueous solution for swelling which is known in the art can be used without particular limitation. For example, water (pure water, deionized water) can be used alone, and when a small amount of glycerin or potassium iodide is added thereto, the polymer film is swollen. At the same time, it can also improve the processability. Preferably, the content of glycerin is 5% by weight or less based on 100% by weight of water, and the content of potassium iodide is 10% by weight or less.

The temperature of the swelling tank is not particularly limited, but may be 20 to 45 ° C, for example, 25 to 40 ° C.

The execution time (swelling tank immersion time) of the swelling step can be performed without any particular limitation, and can be, for example, 180 seconds or less, preferably 90 seconds or less. When the immersion time is in the above range, swelling can be suppressed to an excessively saturated state, and cracking due to softening of the film for forming a polarizer can be prevented, and adsorption of iodine in the dyeing step becomes uniform, and the degree of polarization can be improved.

The swelling step and the stretching step may be simultaneously performed, and in this case, the stretching ratio may be about 1.1 to 3.5 times but is not limited thereto, and preferably 1.5 to 3.0 times. When the elongation ratio is less than 1.1 times, wrinkles may occur, and when it exceeds 3.5 times, the initial optical characteristics may become weak.

<Staining step>

In the dyeing step, the film for forming a polarizer is immersed in a dyeing tank filled with an aqueous solution for dyeing containing a dichroic substance such as iodine to adsorb iodine to the film for forming a polarizer.

As the aqueous solution for dyeing, an aqueous solution for dyeing known in the art can be used without particular limitation, and water, a water-soluble organic solvent or a mixed solvent of these and iodine can be contained. The content of iodine may be from 0.4 to 400 mmol/L in the aqueous solution for dyeing, but is not limited thereto, and is preferably from 0.8 to 275 mmol/L, and most preferably from 1 to 200 mmol/L.

The aqueous solution for dyeing may further contain an iodide as a co-solvent in order to enhance the dyeing efficiency. As the iodide, an iodide known in the art may be used without limitation, and may contain, for example, selected from the group consisting of potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, and iodine. Phlegm, At least one of the group consisting of calcium iodide, tin iodide, and titanium iodide is preferably potassium iodide from the viewpoint of a large solubility of water. The content of the iodide may be from 0.01 to 10% by weight, based on 100% by weight of water, but is not limited thereto, and is preferably from 0.1 to 5% by weight.

Moreover, in order to increase the content of the iodine complex in the film for forming a polarizer, it is possible to add 0.3 to 5% by weight of boric acid to 100% by weight of water in the dyeing tank, but the invention is not limited thereto. When the boric acid in the dyeing tank is less than 0.3% by weight, the increase in the content of PVA-I ₃ ^- complex and PVA-I ₅ ^- complex may have no effect. When the boric acid in the dyeing tank is higher than 5% by weight, the membrane is broken. The danger may become higher.

The temperature of the dyeing tank may be 5 to 42 ° C, but is not limited thereto, and preferably 10 to 35 ° C. Further, the immersion time of the film for forming a polarizer in the dyeing tank is not particularly limited, and may be 1 to 20 minutes, preferably 2 to 10 minutes.

In the present invention, the dyeing step and the stretching step may be simultaneously performed. In this case, the stretching ratio may be 1.01 to 2.0 times, but is not limited thereto, and preferably 1.1 to 1.8 times.

Further, the cumulative stretching ratio including the swelling and the dyeing step up to the dyeing step may be 1.2 to 4.0 times. When the cumulative stretching ratio is less than 1.2 times, wrinkles of the film may occur and the appearance may be poor. When the cumulative stretching ratio exceeds 4.0 times, the initial optical characteristics may become weak.

<Crosslinking step>

Cross-linking step for dyeing iodine molecules by physical adsorption The film is not impaired by the external environment, and the dyed polarizer forming film is immersed in the aqueous solution for crosslinking to fix the adsorbed iodine molecules.

Iodine which is a dichroic dye, when the crosslinking reaction is insufficient, there is a case where the iodine molecule is detached due to the moist heat environment, and a sufficient crosslinking reaction is required. Further, in order to align the iodine molecules between the molecules and the molecules of the film for forming a polarizer and to improve the optical characteristics, the maximum extension ratio can be extended in the crosslinking step.

In the method for producing a polarizer of the present invention, the crosslinking step includes a first crosslinking step and a second crosslinking step, and in the step of one or more of the first and second crosslinking steps, a boron compound-containing compound may be used. Aqueous solution is used in combination. Thereby, the optical characteristics and color durability of the polarizer can be improved.

The cross-linking aqueous solution known in the art can be used without any particular limitation. For example, it may contain water belonging to a solvent, a boron compound such as boric acid or sodium borate, or may further contain an organic solvent which is miscible with water and Iodide.

The boron compound imparts short crosslinks and rigidity to the polarizer, and suppresses the wrinkles in the step of the film, thereby improving the rationality of the film and exerting the function of forming the iodine alignment of the polarizer.

The content of the aforementioned boron compound may be a content known in the art, for example, it may be 1 to 10% by weight, preferably 2 to 6% by weight based on 100% by weight of water. When the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced and it is difficult to impart rigidity to the polarizer. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated. The crosslinking reaction of the organic crosslinking agent is difficult to carry out effectively.

In this step, the iodide can be used to maintain the uniformity of the polarization of the polarizer in the plane, and can also be used to prevent the desorption of the dyed iodine. The iodide may be the same as the user of the dyeing step described above, and the content of the iodide may be 0.05 to 15% by weight with respect to 100% by weight of water, but is not limited thereto, and preferably 0.5 to 14% by weight. When the content is less than 0.05% by weight, the iodine ions in the film may be detached to increase the transmittance of the polarizer. When the content exceeds 15% by weight, the iodide ions in the aqueous solution may permeate the film to allow the polarizer to be worn. The penetration rate is reduced.

In the present invention, the temperature of the crosslinking tank may be 20 to 70 ° C, but is not limited thereto. The immersion time of the film for forming a polarizer in the cross-linking groove may be from 1 second to 15 minutes, but is not limited thereto, and is preferably from 5 seconds to 10 minutes.

The crosslinking step of the present invention comprises the first and second crosslinking steps and is carried out together with the stretching step.

The extension ratio of the first crosslinking step is 2.00 to 3.00 times, preferably 2.20 to 2.80 times. In the first crosslinking step of the present invention, the film for forming a polarizer is stretched at a high elongation ratio to improve the mechanical properties of the polarizer, and the film for forming a polarizer is prevented from being broken in the subsequent second crosslinking step. When the elongation ratio of the first crosslinking step is less than 2.00 times, the target alignment degree cannot be exhibited, and thus the mechanical properties cannot be ensured. When the elongation exceeds 3.00 times, the shrinkage force in the absorption axis direction may increase.

Further, the elongation ratio of the second crosslinking step is 1.00 or less, preferably 0.80 to 1.00, more preferably 0.85 to 1.00. The second crosslinking step of the present invention relaxes the stress generated by the first crosslinking step The step of preventing the crack of the film for forming a polarizer and reducing the contraction force in the direction of the absorption axis. When the elongation ratio of the second crosslinking step exceeds 1.00, the film may be broken and the shrinkage force in the absorption axis direction may increase.

Further, the cumulative stretching ratio of the first and second crosslinking steps may be 1.5 to 3.0 times, preferably 1.98 to 2.8 times. When the cumulative stretching ratio is less than 1.5 times, the alignment effect of the film for forming a polarizer may be insufficient. When the thickness exceeds 3.0, the stress due to the elongation increases, and the contraction force in the absorption axis direction may increase.

<Complementary color step>

In the complementary color step, the iodine complex located between the molecule and the molecule in the film for polarizing film formation in which the iodine complex is physically adsorbed is aligned to the vicinity of the cross-linking of the boric acid to stabilize the iodine complex. Further, through the complementary coloring step, color correction can be performed on the film for polarizing film formation in which the dyeing of the iodine complex in the crosslinking step is insufficient.

The aqueous solution for complementary color in the color-retaining step may contain, for example, water belonging to a solvent and a boron compound such as boric acid, and may further contain an organic solvent and an iodide which are mutually soluble with water.

In the present invention, the boron compound imparts a short crosslink bond and a rigidity to the polarizer, and the wrinkle is suppressed in the step of the film, so that the film is rationally raised, and the iodine alignment of the polarizer can be exhibited.

The content of the aforementioned boron compound may be from 1 to 10% by weight based on 100% by weight of water, but is not limited thereto, and is preferably from 2 to 6% by weight. When the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced and it is difficult to impart rigidity to the polarizer. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated. The crosslinking reaction of the organic crosslinking agent is difficult to carry out effectively.

In this step, the iodide can be used to maintain the uniformity of the polarization of the polarizer in the plane, and can also be used to prevent the desorption of the dyed iodine. The iodide may be used in the same manner as the user of the aforementioned dyeing step, and the content of the iodide may be 0.05 to 15% by weight based on 100% by weight of water, but is not limited thereto, and preferably 0.5 to 11% by weight. When the content is less than 0.05% by weight, the iodine ions in the film may be detached to increase the transmittance of the polarizer. When the content exceeds 15% by weight, the iodide ions in the aqueous solution may permeate the film to allow the polarizer to be worn. The penetration rate is reduced.

In the present invention, the temperature of the complementary color tank may be 20 to 70 °C. The immersion time of the film for forming a polarizer in the complementary color groove may be from 1 second to 15 minutes, but is not limited thereto, and is preferably from 5 seconds to 10 minutes.

The complementary color step of the present invention is carried out together with the stretching step. In this case, the extension ratio of the complementary coloring step is higher than the stretching ratio of the second crosslinking step and lower than the stretching ratio of the first crosslinking step. The complementary color step of the present invention achieves a high degree of alignment by extending the film for polarizing film formation at a relatively high elongation ratio, and can maintain a small contraction force in the absorption axis direction while improving optical characteristics.

The extension of the complementary color step may be from 1.01 to 1.25 times, preferably from 1.05 to 1.20 times, more specific examples. The effect of the aforementioned complementary coloring step can be excellently exhibited in the aforementioned stretching ratio range. Extended ratio When the amount is 1.01 times, there is a possibility that the stability of the iodine complex and the degree of alignment of the film for forming a polarizer become lower. When the thickness exceeds 1.25 times, the film may be broken due to excessive elongation, and productivity may be high. reduce.

<Extension step>

In the present invention, the stretching step may be carried out simultaneously with the crosslinking step and the complementary color step, or may be carried out together with other steps, or may be additionally performed as another step.

According to the production method of the present invention, the total cumulative elongation of the polarizer is preferably 5.0 times or more, preferably 5.0 to 7.0 times, more preferably 5.3 to 6.0 times.

In the present specification, the "cumulative stretch ratio" means the product of the elongation ratio in each step.

<Water washing step>

The method for producing a polarizer according to the present invention may further comprise a water washing step, if necessary, immersing the film for forming a polarizer for crosslinking and stretching in a washing tank filled with an aqueous solution for washing, until the water washing step In the step, unnecessary residues such as boric acid adhered to the film for forming a polarizer are removed.

In the present invention, the aqueous solution for water washing can be used without any particular limitation, and the aqueous solution for water washing known in the art can be, for example, water, and iodide can be further added thereto, but is not limited thereto.

In the present invention, the temperature of the water washing tank may be 10 to 60 ° C. However, it is not limited thereto, and it is preferably 15 to 40 °C.

The water washing step may be omitted, or may be performed at the completion of the steps before the water washing step such as the dyeing step or the crosslinking step. Further, the number of repetitions may be repeated one or more times, and the number of repetitions is not particularly limited.

<Drying step>

In the manufacturing method of the present invention, the drying step is a step of drying the film for forming a water-washed polarizer, and the neck-in by drying causes the alignment of the dyed iodine molecules to be improved. A step of obtaining a polarizer excellent in optical characteristics. Furthermore, the internal contraction means that the width of the film is narrowed.

As the drying method, a drying method well known in the art can be used without limitation, and for example, natural drying, hot air drying, air dry, heat drying, far infrared drying, microwave drying, or the like can be used, and the recent use only makes The water in the film is activated and dried by microwave drying, and is usually mainly dried by hot air.

The execution temperature of the hot air drying is not particularly limited. However, in order to prevent deterioration of the polarizer, it is preferably carried out at a relatively low temperature, and may be, for example, 20 to 90 ° C, preferably 85 ° C or lower, more preferably 80 ° C or lower.

The execution time of the hot air drying described above is not particularly limited and may be, for example, 1 to 10 minutes.

The polarizer of the present invention can be provided as a polarizing plate by bonding a polarizer protective film on at least one side.

The type of the protective film is not particularly limited as long as it is excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and isotropic property. In addition, specific examples include polyester resins such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate; and diethylcellulose. , cellulose resin such as triacetonitrile cellulose; polycarbonate resin; polyacrylic resin such as poly(methyl) acrylate or poly(methyl) acrylate; polystyrene, acrylonitrile-styrene a styrene resin such as a copolymer; a polyolefin resin such as a polyethylene, a polypropylene, a ring system or a polyolefin having a norbornene structure, or an ethylene propylene copolymer; a polyamide resin such as nylon or an aromatic polyamide;醯imino resin; polyether oxime resin; lanthanide resin; polyether ketone resin; polyphenylene sulfide resin; vinyl alcohol resin; vinylidene chloride resin; vinyl butyral resin; A film composed of a blend of the above thermoplastic resin may be used as the film composed of a thermoplastic resin such as an ester resin or a polyoxymethylene resin or an epoxy resin. Further, a film formed of a thermosetting resin such as (meth)acrylic acid, urethane-based, epoxy-based or fluorene-based or ultraviolet-curable resin can also be used. Among these, in view of polarizing characteristics and durability, a film composed of a cellulose resin having a surface saponified with a base or the like is particularly preferable. Further, the protective film may be a function having the following optical layer.

The structure of the polarizing plate is not particularly limited, and various types of optical layers which can satisfy the necessary optical characteristics can be laminated on the polarizer. For example, it may have a structure in which a protective film for protecting a polarizer is provided on at least one area of the polarizer; a hard coat layer, an anti-reflection layer, and an adhesion prevention layer are laminated on at least one side of the polarizer or the protective film; Preventing the structure of the surface treatment layer such as the diffusion layer and the anti-glare layer; aligning the alignment liquid crystal layer or other functional film on at least one side of the polarizer or the protective film Construction. Further, as a polarizing conversion device for forming various image display devices, an optical film, a reflector, a transflective reflector, a wavelength plate including a 1⁄2 wavelength plate or a 1⁄4 wavelength plate (including λ) may be laminated. One or more of the phase difference plate, the viewing angle compensation film, and the brightness enhancement film of the plate) are configured as an optical layer. More specifically, it is preferably a polarizing plate having a structure in which a protective layer is formed on one of the polarizing plates, and a reflective polarizing plate or a semi-through layer in which a reflector or a transflective reflector is laminated on the protective film of the laminated layer. A translucent polarizing plate; an elliptical or circular polarizing plate in which a phase difference plate is laminated; a wide viewing angle polarizing plate in which a viewing angle compensation layer or a viewing angle compensation film is laminated; or a polarizing plate in which a brightness increasing film is laminated.

The bonding of the polarizer to the polarizer protective film can be carried out using an adhesive composition. The bonding of the polarizer using the adhesive composition to the protective film can be carried out by an appropriate method, and examples thereof include a casting method, a bar coating method, a gravure coating method, a die coating method, and a dip coating method. A method of applying an adhesive composition to the adhesion surface of a polarizing film and/or a protective film, and superimposing the two, such as a cloth method or a spray method. The casting method is a method in which a polarizer or a protective film belonging to a coated object is slightly perpendicular, slightly horizontal, or obliquely inclined therebetween, and an adhesive composition is applied to the surface thereof.

After the adhesive composition was applied, the polarizer and the protective film were sandwiched by a roll to be joined.

Further, in order to improve the adhesion, the surface of the polarizer and/or the protective film may be subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment. In terms of saponification, A method of immersing in an aqueous solution of a base such as sodium hydroxide or potassium hydroxide can be mentioned.

After the polarizer and the polarizer protective film are laminated, a drying treatment is performed. The drying treatment is carried out, for example, by spraying hot air, and the temperature at this time is appropriately selected in the range of 50 to 100 degrees. The drying time is usually 30 to 1,000 seconds.

The polarizing plate of the present invention can be applied not only to a general liquid crystal display device but also to various image display devices such as an organic electric field light-emitting display device (OLED), a plasma display device, and an electric field emission display device.

(Example)

In the following, preferred embodiments are suggested to facilitate the understanding of the present invention, but the embodiments are merely illustrative of the present invention and do not limit the scope of the patent application, and those skilled in the art will recognize the scope and technology of the present invention. Various changes and modifications can be made to the embodiments within the scope of the ideas, and such changes and amendments are of course within the scope of the patent application in this case.

<Example 1>

A transparent unstretched polyvinyl alcohol film (PE60, KURARAY Co., Ltd.) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 25 ° C for 1 minute and 20 seconds to swell (swelling step), and then immersed in iodine. 1.25 mM/L was dyed in an aqueous solution for dyeing containing 30.5% by weight of potassium iodide and 0.3% by weight of boric acid at 30 ° C for 2 minutes and 30 seconds (dyeing step). At this time, in the swelling and dyeing steps, the stretching ratio was extended by about 1.7184 times and about 1.5214 times, respectively, and the cumulative stretching ratio until the dyeing groove was 2.614 times. Then, immersed in 100% by weight of water relative to water containing iodine Potassium chloride (13.9 wt%) and boric acid 3% by weight of 56 ° C in an aqueous solution for crosslinking were crosslinked for 26 seconds (first crosslinking step) while extending at an extension ratio of 2.36 times. Then, it was immersed in an aqueous solution for cross-linking containing 56.9% by weight of potassium iodide and 3% by weight of boric acid at 56 ° C for 20 seconds to be crosslinked (second crosslinking step) while extending at 0.90 times. More than extension.

Then, it was immersed in an aqueous solution for complementary color containing 40% by weight of potassium iodide and 40% by weight of boric acid in 100% by weight of water, and was extended for 1.08 times at the same time (filling step).

At this time, the total cumulative elongation ratio of the swelling, dyeing, cross-linking, and complementary color steps was made six times. After completion of the crosslinking, the polyvinyl alcohol film was washed with deionized water (water washing step), and then dried in an oven at 80 ° C for 5 minutes (drying step) to prepare a polarizing plate having a transmittance of 42.5%. The thickness of the polarizer was 23 μm.

A polarizing plate was produced on a double-area layer of triacetyl cellulose (TAC) film of the produced polarizer.

<Examples 2 to 10 and Comparative Examples 1 to 6>

A polarizing plate was produced in the same manner as in Example 1 except that the elongation ratio was adjusted as described in Table 1 below.

<Test example>

The physical properties of the polarizer produced in the above examples and comparative examples were measured by the following methods, and the results are shown in Table 2 below.

<1. Optical characteristics (polarity)>

After the produced polarizer was cut into a size of 4 cm × 4 cm, the transmittance was measured using an ultraviolet-visible spectrometer (V-7100, manufactured by JASCO Corporation). At this time, the degree of polarization is defined by the following formula 2.

[Equation 2] Polarization degree (P) = [(T _{1 -} T ₂ ) / (T ₁ + T ₂ )] ^1/2 (wherein, T ₁ is a pair of polarizers arranged in a state in which the absorption axes are parallel The parallel transmittance obtained, T ₂ is an orthogonal transmittance obtained when a pair of polarizers are arranged in a state in which the absorption axis is orthogonal.

<2. Orientation>

After the manufactured polarizer was cut into a size of 4 cm × 4 cm, the IR beam was polarized using a polarizing ATR apparatus (VeeMAX III, PIKE, incident angle: 45°) so that the polarized IR beam and the MD of the polarizer sample were polarized. The absorbance (A _MD ) (Nicolet Continuum XL, Thermo Corporation) was measured by FT-IR in a manner in which the directions (absorption axis directions) were parallel. Then, the absorbance (A _TD ) was measured by FT-IR so that the polarized IR beam was parallel to the TD direction (the transmission axis direction) of the polarizer sample.

In the MD and TD directions, the absorbance at 1290 cm ^-1 showing the difference in absorbance was measured.

The measured absorbance was substituted into the above formula 1 to obtain an alignment degree.

<3. Contraction force>

Here, the contraction force in the direction of the absorption axis per 2 mm width of the direction of the transmission axis of the polarizer was measured. The polarizer produced in the examples and the comparative examples was cut into a size of 3.0 cm (absorption axis direction) × 2 mm (penetration axis direction), and then measured by DMA Q800 (Dynamic mechanical analyzer, TA). The contraction force in the direction of the absorption axis at °C for 4 hours. At this time, in order to maintain the polarizer in a flat state before the measurement, the measurement was performed with a minimum load in the thickness direction of the polarizer.

Referring to Table 2, it was confirmed that the polarizer of the present invention satisfies both the high alignment degree and the contraction force in the absorption axis direction, and the polarization degree is also excellent.

However, in the case of the comparative example, it was found that when the degree of polarization is excellent, the contraction force in the absorption axis direction is high, and the contraction force in the absorption axis direction is low, the degree of polarization is low.

Claims (7)

A polarizer having an alignment degree of 0.250 to 0.400 and a contraction force in an absorption axis direction of 3.5 N/2 mm or less, and the above-mentioned alignment degree is obtained by the following formula 1: Wherein, A _MD-based polarizing plate of the absorbance of the infrared light absorption axis of the polarizer, A _TD-based absorbance of the polarizer in the transmission axis direction of the polarization of the infrared light, A _large A _MD system and the higher of A _TD Absorbance, A _small is the absorbance of the lower of A _MD and A _TD . The polarizer according to claim 1, wherein the orientation is 0.300 to 0.400. A method for producing a polarizer comprising the steps of swelling, dyeing, stretching, crosslinking, complementary color, and drying of a film for forming a polarizer, wherein the crosslinking step comprises extending the film for forming a polarizer to 2.00 to 3.00 times the first. a crosslinking step and a second crosslinking step of extending the film for forming a polarizer to 1.00 times or less after the first crosslinking step, wherein the complementary coloring step is higher than the stretching ratio of the second crosslinking step The film for polarizer formation is extended in the extension ratio of the first crosslinking step. The method for producing a polarizer according to claim 3, wherein in the second crosslinking step, the film for forming a polarizer is extended to 0.85 to 1.00 times. The method for producing a polarizer according to the third aspect of the invention, wherein the film for forming a polarizer is extended from 1.01 to 1.25 times. A polarizing plate comprising the polarizer described in claim 1 or 2, and a polarizer protective film bonded to at least one side of the polarizer. An image display device comprising the polarizing plate described in claim 6 of the patent application.